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Production technology of seamless steel tube for nuclear power
- Mar 31, 2018 -

Seamless steel tube for nuclear industry.

Yangzhou Steel Pipe Co., Ltd. commissioned by the Suzhou Institute of Thermal Research Co., Ltd. on the trial production of nuclear power conventional island with WB36CN1, P22 high-pressure seamless steel pipe for pipeline welding and welding process assessment. Yangzhou Steel Pipe Co., Ltd. using oblique rolling perforation + cold drawn sizing process of nuclear power wb36cn1, P22 seamless steel pipe surface quality, geometrical size and physical and chemical properties and other indicators are met gb24512.2-2009 "nuclear power plant Seamless steel tube 2nd: alloy Steel seamless steel pipe" technical requirements, In the same kind of steel pipe in the leading level.

1 Welding process Assessment

The test include WB36CN1 steel cold crack test, reheat crack test, P22 steel cold crack test, WB36CN1 steel pipe tig/smaw/saw Combined welding process evaluation, P22 steel pipe TIG/SMAW and Tig/smaw/saw combined welding process evaluation, Welding Process Assessment Implementation dl/t1117-2009 "Nuclear power plant conventional Island welding process assessment code."

Test results for weldability and welding process evaluation of WB36CN1 steel tube.

For WB36CN1 Steel pipe, the highest hardness method in heat affected zone, cold crack test method of oblique y groove, cold crack test method of Bolt, the results show that under preheating 160 ℃ condition, the highest hardness of heat affected zone is lower than that of 350hv1, oblique y groove weld surface and section has not found crack, The critical fracture stress exceeds the yield strength of wb36cn1 steel, so preheating 160 ℃ can prevent the cold crack from producing. The preheating temperature is consistent with the 15NI1MNMONBCU steel pipe recommended in the relevant standard.

WB36CN1 Steel in 590 ℃ and 610℃ two temperature insulation 3h thermal crack test respectively, oblique y groove weld surface and section did not find any form of crack, it is explained that Yangzhou Cheng de Steel Pipe Co., Ltd. production WB36CN1 steel in 580-620 ℃ range, The thermal crack sensitivity under stress condition is insufficient to cause the reheat crack to produce, 590 ℃ and 610℃ two temperature are suitable for the heat treatment after welding.

The evaluation results of welding process of WB36CN1 steel with Tig/smaw/saw combined welding method show that the welding process of the steel pipe matching imported welding material is excellent, the specimen is qualified by magnetic powder and radiographic nondestructive testing, and the quality of welding process meets the standard requirements. After welding and after welding high-temperature tempering of welded joints room temperature strength, high temperature strength, impact toughness to meet the gb24512.2-2009 of raw material performance requirements, meet dl/t1117-2009 requirements. The microstructure of welded joint is ferrite + Bainite, the microstructure is not found in microscopic state, and the highest hardness of joint weld and heat affected zone is higher than that of base metal, but none of them exceed 270HB, which accords with dl/t1117-2009 requirement, and the full thickness bending does not find any form of crack. Weld main elements content and raw materials, impurity element content control at low level, the whole welding process evaluation test results are in line with dl/t1117-2009 requirements, so that the WB36CN1 steel welding process evaluation qualified.

2 Test results for weldability and welding process evaluation of P22 steel Tube.

For the P22 steel pipe, through the heat affected zone the highest hardness method, the cold crack test method of oblique y groove and the test of cold crack test of the bolt, the results show that: under the condition of Preheating 80 ℃, the highest hardness of heat affected zone is lower than 350HV1, but the preheating temperature has been increased to 250 ℃, the highest hardness is still close to 320hv1, the same preheating condition , no cracks were found on the weld surface and section of the Oblique Y groove, the highest hardness method in heat affected zone and cold crack test method of oblique y groove The result is that preheating 80 ℃ can prevent cold crack, and the critical fracture stress is far exceeding the yield strength of P22 steel when preheating temperature is 200 ℃ and 150 ℃. The results show that preheating 150 ℃ by the bolt test can prevent the cold crack from producing. Three kinds of test results show that the preheating temperature of P22 steel to prevent cold crack should be lower than 150 ℃, the data is lower than the recommended 200-300 ℃ preheating range, so Yangzhou Cheng de Steel Pipe Co., Ltd. the cold crack sensitivity of P22 steel for nuclear power production is better than that of similar steels.

The evaluation results of welding process of P22 steel with Tig/smaw/saw combined welding method show that the steel pipe matching domestic and imported welding materials has excellent welding process performance, the specimen is qualified by magnetic powder and radiographic nondestructive testing, the quality of welding process meets the standard requirements, and the welding joints at high temperature temper after welding are at room temperature strength, High-temperature strength and impact toughness meet the requirements of GB 24512.2-2009 for raw material performance and meet dl/t1117-2009 requirements. The microstructure of welded joint is ferrite + Bainite, the microstructure is not found in microscopic state, and the highest hardness of joint weld and heat affected zone is higher than that of base metal, but none of them exceed 270HB, which accords with dl/t1117-2009 requirement, and the full thickness bending does not find any form of crack. Weld main elements content and raw materials, impurity element content control at low level, the whole welding process evaluation test results are in line with dl/t1117-2009 requirements, so that the P22 steel welding process evaluation qualified.

The results of welding process evaluation of P22 steel by TIG/SMAW combined manual welding show that the steel pipe matching the welding process of domestic wire and electrode is excellent, the specimen is qualified by magnetic powder and radiographic nondestructive testing, the quality of welding process meets the standard requirements, and after welding and welding high-temperature tempering welding joints room temperature strength, high temperature strength, The impact toughness meets the requirements of the GB 24512.2-2009 for raw material performance, meets the dl/t1117-2009 requirements, the welded joint microstructure is Ferrite + bainite, the microstructure is not found in the microscopic state, no abnormal microstructure appears, and the weld seam and heat affected zone of the joint are higher than the base metal, But are not more than 270HB, in line with dl/t1117-2009 requirements, the full thickness of the bending did not find any form of crack, the main elements of the weld and raw materials, impurities content control at low levels, the entire welding process assessment test results are in line with dl/t1117-2009 requirements, P22 Steel welding process qualification.